The present invention relates to preservatives for certain organic fluids which are prone to microbial degradation or contamination during use or storage.
The fluids referred to are those which are or become, under conditions of use or storage, a mixture of an organic component and a water component wherein the water is either dissolved in the organic component or vice versa or where water forms an oil/water interface with the organic component, and which supports and promotes microbial growth leading to contamination and/or degradation of the fluid. More particularly the invention is useful in at least 2 types of fluids: functional fluids and liquid hydrocarbon fuels.
As used herein the term "functional fluid" refers to fluids such as hydraulic fluid, brake fluid, and metal working fluids, such as cutting fluids. The liquid hydrocarbon fuels include diesel fluid, jet fuel, general aviation fuel, and heating oil. For purposes of simplicity the present invention is defined with particular reference to metal working fluids, but is understood to be applicable to the other functional fluids and fuels unless a contrary intent is specifically set forth herein.
The term "metal working fluids" as used herein are those fluids discussed in "Metal Working Lubricants", E. L. H. Bastian, McGraw Hill Co., 1951, pp. 5-56, which will support microbial growth under conditions of normal use. For purposes of convenience these fluids may be divided into two types, the straight oils and the so-called water soluble fluids. Straight oils are basically a petroleum oil, with or without additives. The principle component may be a naphthenic or paraffinic oil. The straight oils are not miscible with water and thus, when exposed to moisture during use or storage, form an interface therewith which supports growth of microorganisms. The water soluble fluids may be subdivided into at least three major types including Chemical Fluids, Emulsions, and Semi-Chemical Fluids as described in CUTTING AND GRINDING FLUIDS: Selection and Application, American Society of Tool and Manufacturing Engineers, Dearborn, Michigan, 1967, pp. 1-4.
Chemical Fluids, also known as "Synthetic Fluids", are those which do not form emulsions when diluted for use, which may or may not contain surfactants, and which contain no mineral oil or other water insoluble lubricant component.
Emulsions, also known as "Water Miscible Fluids", "Water Soluble Oils", or "Soluble Oils", are emulsions of oil droplets (mineral, paraffinic or naphthalenic) in water. These fluids generally contain 50 to 75% oil with the balance being emulsifiers, additives, coupling agents, corrosion inhibitors, etc. The emulsifiers may be, for example, petroleum sulfonates, amine soaps, rosin soaps, naphthenic acids, etc. Coupling agents may be, for example, complex alcohols or nonionic surfactants, etc. Particle size of the oil droplets is at least 0.1.mu. and is generally 2-5.mu. when diluted for use.
Semi-Chemical Fluids, also known as "Semi-Synthetic Fluids", contain less oil than emulsions, generally 10 to 45%, higher amounts of emulsifiers and additives and up to about 20% water. Particle size of the oil droplets is generally in the range of 0.1.mu. to 1.0 m.mu. when diluted for use.
Any of these fluid types may contain active sulfur, phosphorus and chlorine compounds to increase efficiency under severe machining conditions. These additives are called Extreme Pressure (E.P.) additives and may take the form of sulfurized fat, chlorinated paraffin, phosphates or the like.
These metal working fluids when mixed with water are used commercially in large quantities to reduce friction in metal working operations such as cutting, threading, grinding, polishing and the like, and to dissipate heat generated as a result thereof. Since large quantities are employed, it is desirable to reuse the fluids as long as possible. In this regard one of the major problems for users of these fluids has been preventing microbial contamination and/or degradation upon continued use.
Manufacturers and others have explored numerous biocides for use in metal working fluids and many of these are reported in the patent literature. Of those which are commercially available, the following are commonly used:
1. MILIDIN TI-10, DeMille Chemical Co., believed to comprise about 93% hydroiodide salt of mixed ethylene diamine monoethylene glycol ether; PA1 Bacteria PA1 Molds PA1 Yeasts
2. GROTAN, Lehn & Fink, 78.5% Hexahydro-1,3,5,tris-(2-hydroxyethyl)-triazine;
3. VANCIDE-TH, R. T. Vanderbilt Co., Hexahydro-1,3,5-triethyl-triazine.
While these exhibit a certain degree of efficacy in metal working fluids, they lose their ability to protect against growth of offending organisms after a limited period of time.
On the other hand, a desirable biocide for protecting these fluids against microbial attack should preserve the fluid over extended periods of time. It should also be compatible with a large majority of the fluids which are presently in commercial use and should prevent the dermatitis which frequently occurs due to handling of or exposure to contaminated fluids.
Because of the great diversity of additives found in commercially available metal working fluids, it is clearly impossible to find a universal preservative which will be effective for all such fluids. We have found, however, that selected 1,10-phenanthrolines are surprisingly effective in preventing microbial contamination of many such fluids over extended periods of time.
1,10-Phenanthrolines are known and commercially available. They are usually prepared by a Skraup reaction or a modified or related Skraup reaction which involves heating a primary aromatic amine having at least one unsubstituted ortho position with glycerol, sulfuric acid and an oxidizing agent. If the aromatic amine is a monoamine, the resultant compound is a substituted quinoline which may then be further reacted to form the phenanthroline. The reaction of an aromatic diamine such as 3,4-tolylene diamine with 2 moles of glycerol also yields 1,10-phenanthroline substituted in the 5 position.
Another method of preparing 1,10-phenanthrolines is to first prepare 8-amino-quinoline and then react this under Skraup reaction condition as indicated above. These methods and various modifications thereof for manufacturing 1,10-phenanthrolines are more completely discussed and set forth in U.S. Pat. No. 3,389,143 which is incorporated herein by reference insofar as it is relevant to the manufacture and purification of 1,10-phenanthrolines.
It is also known that phenanthrolines, including various 1,10-phenanthrolines exhibit varying degrees of microbiological activity. These compounds have not previously been employed as preservatives in organic fluids. We have found that certain of the 1,10-phenanthrolines are remarkably effective in this application.